Fix kaleido image export bug

[quinten-goens]

Description of the problem

The code needs access to the Python sys module to run. Otherwise it gives a missing package error. The following code generates the error:

# Install latest development version
devtools::install_github("ropensci/plotly")

# Import libraries
library(plotly)
library(reticulate)

# Create example plot
fig <- plot_ly(midwest, x = ~percollege, color = ~state, type = "box")

# Simulate a conda environment to use Kaleido
reticulate::install_miniconda()
reticulate::conda_install('r-reticulate', 'python-kaleido')
reticulate::conda_install('r-reticulate', 'plotly', channel = 'plotly')
reticulate::use_miniconda('r-reticulate')

# Save the figure
save_image(fig,file="image.png", height=500, width=700)

The error is:

> save_image(fig,file="image.png", height=500, width=700)
Error in py_run_string_impl(code, local, convert) : 
  NameError: name 'sys' is not defined

This has been solved by importing the sys package in the Python command in the correct place, see commit.

Installing the bugfix

You can install the version with the bugfix and rerun the code like this:

# Reinstall latest development version which includes the bugfix
devtools::install_github("quinten-goens/plotly.R@fix/kaleido-export-bug")

# Import libraries
library(plotly)
library(reticulate)

# Create example plot
fig <- plot_ly(midwest, x = ~percollege, color = ~state, type = "box")

# Simulate a conda environment to use Kaleido
reticulate::install_miniconda()
reticulate::conda_install('r-reticulate', 'python-kaleido')
reticulate::conda_install('r-reticulate', 'plotly', channel = 'plotly')
reticulate::use_miniconda('r-reticulate')

# Save the figure
save_image(fig,file="image.png", height=500, width=700)

The export works now.

[cpsievert]

Thanks!